Biology subjects

Zemp, N.

Publications and source records attributed to Zemp, N..

7 recordsLinked to original sources

bioRxiv2023

Evolution of sex-biased gene expression during transitions to separate sexes in the Silene genus

Sexual dimorphism is widespread among species with separate sexes and its extent is thought to be governed by the differential expression of thousands of genes between males and females (known as Sex-Biased Genes, hereafter SBGs). SBGs have been studied in numerous species, but rarely in a comparative way, which curtails our understanding of their evolution, especially during multiple independent transitions to separate sexes. We sequenced the transcriptomes of nine dioecious species, two gynodioecious species (separate females and hermaphrodites) and two hermaphrodite species from the Silene genus. Our dataset provides access to three independent transitions to dioecy (dating from less than 1 Myo to about 11 Myo). We demonstrated that male-biased expression emerges first during a transition to separate sexes, later followed by female-biased genes. Furthermore, we showed that, despite a mixture of selective regimes, positive selection significantly affects the evolution of some SBGs. Overall, this study provides new insights on the causes of SBG evolution during transitions to separate sexes. TeaserThis study describes the evolution of sex-biased gene expression during a transition to separate sexes in plants.

evolutionary biology↗

bioRxiv2021

Genetic diversity at putatively adaptive but not neutral loci in Primula veris responds to recent habitat change in semi-natural grasslands

Recent habitat change in semi-natural grasslands due to a lack of management has been shown to affect the genetic diversity of grassland plants. However, it is unknown how a change in local environment affects genetic diversity at adaptive loci. We applied RADseq (restriction-site associated DNA sequencing) to extract > 3,000 SNPs across 568 individuals from 32 Estonian populations of Primula veris, a plant species common to semi-natural grasslands. We evaluated the effect of recent grassland overgrowth following management abandonment on the genetic diversity at putatively neutral and adaptive loci, which we distinguished by applying three methods, i.e., linear and categorical environmental association analyses, and an FST outlier test. For validation, we randomised the genotype to sample assignments. Effects of recent habitat change on genetic diversity differed between neutral and adaptive SNP sets. Genetic diversity assessed at putatively neutral loci was similar in open and overgrown habitats but showed a significant difference between these habitat types at putatively adaptive loci: overgrown (i.e. newly established) habitats exhibited higher genetic diversity at putatively adaptive loci than open (i.e. old) habitats, likely due to the exertion of novel selection pressures imposed by new habitat conditions. This increase in genetic diversity at putatively adaptive loci in the new environment points to currently ongoing selection processes where genetic adaptation to the old habitat is potentially lost through altered allele frequencies. Our study suggests that a recent change in local habitat conditions may not be reflected in neutral loci whereas putatively adaptive loci can inform about potential selection processes.

plant biology↗

bioRxiv2021

Species ecology explains the various spatial components of genetic diversity in tropical reef fishes

Intraspecific genetic diversity should be dependent on species ecology, but the influence of ecological traits on interspecific differences in genetic variation is yet to be explored. Generating sequenced data for 20 tropical reef fish species of the Western Indian Ocean, we investigate how species ecology influences genetic diversity patterns from local to regional scales. We distinguish between the , {beta} and{gamma} components of genetic diversity, which we subsequently link to six ecological traits. In contrast to what is expected by the neutral theory of molecular evolution, we find that the and{gamma} components of genetic diversity are negatively associated with species abundance, which can be explained by larger variance in reproductive success in large populations and/or higher introgression in less frequent species. Pelagic larval duration, an important dispersal trait in marine fishes, is found to be negatively related to genetic {beta} diversity, as expected by theory. We conclude that the neutral theory of molecular evolution may not be sufficient to explain genetic diversity in tropical reef fishes and that additional processes influence those relationships.

genetics↗

bioRxiv2020

A reference transcriptome for the early-branching fern Botrychium lunaria enables fine-grained resolution of population structure

Ferns are the second most dominant group of land plants after angiosperms. Extant species occupy an extensive range of habitats and contribute significantly to ecosystem functioning. Despite the importance of ferns, most taxa are poorly covered by genomic resources. The genus Botrychium belongs to the family Ophioglossaceae, one of the earliest divergent lineages of vascular plants, and has a cosmopolitan distribution with 35 species, half of which are polyploids. Here, we establish a transcriptome for Botrychium lunaria, a diploid species with an extremely large genome with a 1C value of 12.10 pg. We assembled 25,701 high-quality transcripts with an average length of 1,332 bp based on deep RNA-sequencing of a single individual. We sequenced an additional 11 transcriptomes of individuals from two populations in Switzerland, including the population of the reference individual. Based on read mapping to reference transcript sequences, we identified 374,510 single nucleotide polymorphisms (SNPs) segregating among individuals for an average density of 14 SNPs per kb. The transcriptome-wide markers provided unprecedented resolution of the population genetic structure revealing substantial variation in heterozygosity among individuals. We also constructed a phylogenomic tree of 90 taxa representing all fern orders to ascertain the placement of the genus Botrychium. The high-quality transcriptomic resources enable powerful population and phylogenomic studies in an important group of ferns. Significance statementFerns pose substantial puzzles in terms of lifestyles, genome organization and population structure. Progress has been significantly hampered by the lack of genomic resources. Here, we present a transcriptome for Botrychium lunaria, a phylogenetically early-branching fern with an extremely large genome. We show that the new transcriptome improves phylogenetic resolution among early-branching ferns. Based on an additional 11 transcriptomes of the same species, we identify unexpected variation in population-level heterozygosity.

genomics↗

bioRxiv2019

Isolation and comparative genomic analysis of reuterin-producing Lactobacillus reuteri from poultry gastrointestinal tract

Lactobacillus reuteri is a natural inhabitant of selected animal and human gastrointestinal tract (GIT). Certain strains have the capacity to transform glycerol to 3-hydroxypropionaldehyde (3-HPA), further excreted to form reuterin, a potent antimicrobial system. Reuterin-producing strains may be applied as a natural antimicrobial in feed to prevent pathogen colonization of animals, such as in poultry, and replace added antimicrobials. To date, only seven L. reuteri strains isolated from poultry have been characterized which limits phylogenetic studies and host-microbes interactions characterization. This study aimed to isolate L. reuteri strains from poultry GIT and to characterize their reuterin production and antimicrobial resistance (AMR) profiles using phenotypic and genetic methods. Seventy reuterin-producing strains were isolated from poultry crop, faeces and caeca and twenty-five selected for further characterization. Draft genomes were generated for the new 25 isolates and integrated in a phylogenetic tree of 40 strains from different hosts. Phylogenetic analysis based on gene content as well as on core genomes showed grouping of the selected 25 L. reuteri poultry isolates within the poultry/human lineage VI. Strains harbouring pdu-cob-cbi-hem genes (23/25) produced between 156 mM {+/-} 11 and 330 mM {+/-} 14 3-HPA, from 600 mM of glycerol, in the conditions of the test. All 25 poultry strains were sensitive to cefotaxime (MIC between 0.016 and 1 g/mL) and penicillin (MIC between 0.02 and 4 g/mL). Akin to the reference strains DSM20016 and SD2112, the novel isolates were resistant to penicillin, possibly associated with identified point mutations in ponA, pbpX, pbpF and pbpB. All strains resistant to erythromycin (4/27) carried the ermB gene, and it was only present in poultry strains. All strains resistant to tetracycline (5/27) harbored tetW gene. This study confirms the evolutionary history of poultry/human lineage VI and identifies pdu-cob-cbi-hem as a frequent trait but not always present in this lineage. L. reuteri poultry strains producing high 3-HPA yield may have potential to prevent enteropathogen colonization of poultry.

genomics↗

bioRxiv2018

Dioecy in plants: an evolutionary dead end? Insights from a population genomics study in the Silene genus

About 15,000 angiosperm species ([~]6%) have separate sexes, a phenomenon known as dioecy. Early work reported a lower species richness in dioecious compared to non-dioecious sister clades, which was taken to suggest that dioecy might be an evolutionary dead end. More recently, phylogenetic analyses using different methodologies have challenged this conclusion. Here, we used a population genomics approach to look for evidence of evolutionary handicaps of dioecy in the Silene genus at the molecular level. We obtained RNA-seq data of individuals from several populations in 13 closely related species with different breeding systems: seven dioecious, three hermaphroditic and three gynodioecious species. We show that dioecy is associated with increased genetic diversity and a higher selection efficacy both against deleterious and for beneficial mutations while controlling for differences in population size. We conclude that, in the Silene genus, dioecious species bear no sign of mutational burden or upcoming extinction. On the contrary, dioecious species harbor a higher potential for adaptation than their non-dioecious relatives. Our results do not support the evolutionary dead end hypothesis and re-open the question why dioecy is rare in angiosperms.\n\nSignificance statementDioecy (=separate sexes) is much rarer in flowering plants compared to animals and other organisms. The \"dead-end hypothesis\" states that dioecious plant populations might experience evolutionary handicaps such as low seed dispersal (as only 50% of the individuals, the females, contribute), which might cause high genetic drift, low adaptation and ultimately extinction. Here we tested this hypothesis by focusing on the genus Silene and by comparing the population genetics of 13 dioecious and non-dioecious species. We found that dioecious Silene species exhibit lower genetic drift and more adaptation compared to their non-dioecious relatives. Our results thus reject the dead-end hypothesis and re-open the question of why dioecy is rare in flowering plants.

evolutionary biology↗

bioRxiv2017

Maternal X chromosome upregulation in both sexes initiates dosage compensation evolution

This preprint has been reviewed and recommended by Peer Community In Evolutionary Biology (http://dx.doi.org/10.24072/pci.evolbiol.100044).\n\nSex chromosomes have repeatedly evolved from a pair of autosomes1. Consequently, X and Y chromosomes initially have similar gene content, but ongoing Y degeneration leads to reduced Y gene expression and eventual Y gene loss. The resulting imbalance in gene expression between Y genes and the rest of the genome is expected to reduce male fitness, especially when protein networks have components from both autosomes and sex chromosomes. A diverse set of dosage compensating mechanisms that alleviates these negative effects has been described in animals2-4. However, the early steps in the evolution of dosage compensation remain unknown and dosage compensation is poorly understood in plants5. Here we show a novel dosage compensation mechanism in the evolutionarily young XY sex determination system of the plant Silene latifolia. Genomic imprinting results in higher expression from the maternal X chromosome in both males and females. This compensates for reduced Y expression in males but results in X overexpression in females and may be detrimental. It could represent a transient early stage in the evolution of dosage compensation. Our finding has striking resemblance to the first stage proposed by Ohno for the evolution of X inactivation in mammals.

evolutionary biology↗